Cross-correlation of excitation functions for different fragments and different scattering angles in Al-27(F-19, x)y reactions

Excitation functions have been measured for different projectile-like fragments produced in Al-27(F-19,x)y reactions at incident energies from 110.25 to 118.75 MeV in 250 keV steps. Strong cross section fluctuations of the excitation functions are observed. The cross- correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle theta(cm) have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion Collision of Al-27(F-19,x)y.

Prediction of soil organic carbon partition coefficients by soil column liquid chromatography

To avoid the limitation of the widely used prediction methods of soil organic carbon partition coefficients (K-OC) from hydrophobic parameters, e.g., the n-octanol/water partition coefficients (K-OW) and the reversed phase high performance liquid chromatographic (RP-HPLC) retention factors, the soil column liquid chromatographic (SCLC) method was developed for K-OC prediction. The real soils were used as the packing materials of RP-HPLC columns, and the correlations between the retention factors of organic compounds on soil columns (k(soil)) and K-OC measured by batch equilibrium method were studied. Good correlations were achieved between k(soil) and K-OC for three types of soils with different properties. All the square of the correlation coefficients (R-2) of the linear regression between log k(soi) and log K-OC were higher than 0.89 with standard deviations of less than 0.21. In addition, the prediction of K-OC from K-OW and the RP-HPLC retention factors on cyanopropyl (CN) stationary phase (k(CN)) was comparatively evaluated for the three types of soils. The results show that the prediction of K-OC from k(CN) and K-OW is only applicable to some specific types of soils. The results obtained in the present study proved that the SCLC method is appropriate for the K-OC prediction for different types of soils, however the applicability of using hydrophobic parameters to predict K-OC largely depends on the properties of soil concerned. (C) 2004 Elsevier B.V. All rights reserved.

Prediction of soil organic partition coefficients by a soil leaching column chromatographic method

The soil organic partition coefficient (K-oc) is one of the most important parameters to depict the transfer and fate of a chemical in the soil-water system. Predicting K-oc by using a chromatographic technique has been developing into a convenient and low-cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol-water eluents was developed to predict the K-oc of hydrophobic organic chemicals (HOCs), over a log K-oc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent (k(w)') could be obtained by linearly extrapolating capacity factors in methanol-water eluents (k') with various volume fractions of methanol (phi). The important effects of solute activity coefficients in water on k(w)' and K-oc were illustrated. Hence, the correlation between log K-oc and log k(w)' (and log k') exists in the soil. The correlation coefficient (r) of the log K-oc vs. log k(w)' correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log K-oc-log k' correlations were no less than 0.968, with phi ranging from 0 to 0.50. The smaller the phi, the higher the r. Therefore, it is recommended that the eluent of smaller phi, such as water, be used for accurately estimating K-oc. Correspondingly, the r value of the log K-oc-log k(w)' correlation on a reversed-phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict K-oc indirectly from a correlation with k(w)' than the reversed-phase liquid chromatographic (RPLC) one.

Time Correlations Of Pressure In Isotropic Turbulence

The time correlations of pressure modes in stationary isotropic turbulence are investigated under the Kraichnan and Tennekes "random sweeping" hypothesis. A simple model is obtained which predicts a universal form for the time correlations. It implies that the decorrelation process of pressure fluctuations in time is mainly dominated by the sweeping velocity, and the pressure correlations have the same decorrelation time scales as the velocity correlations. These results are verified using direct numerical simulations of isotropic turbulence at two moderate Reynolds numbers; the mode correlations collapse to the universal form when the time separations are scaled by wavenumber times the sweeping velocity, and the ratios of the correlation coefficients of pressure modes to those of velocity modes are approximately unity for the entire range of time separation. (c) 2008 American Institute of Physics.

Pharmacokinetics of sifuvirtide, a novel anti-HIV-1 peptide, in monkeys and its inhibitory concentration in vitro

Aim: To study the pharmacokinetics of sifuvirtide, a novel anti-human immunodeficiency virus (HIV) peptide, in monkeys and to compare the inhibitory concentrations of sifuvirtide and enfuvirtide on HIV-1-infected-cell fusion. Methods: Monkeys received 1.2 mg/kg iv or sc of sifuvirtide. An on-line solid-phase extraction procedure combined with liquid chromatography tandem mass spectrometry (SPELC/MS/MS) was established and applied to determine the concentration of sifuvirtide in monkey plasma. A four-I-127 iodinated peptide was used as an internal standard. Fifty percent inhibitory concentration (IC50) of sifuvirtide on cell fusion was determined by co-cultivation assay. Results: The assay was validated with good precision and accuracy. The calibration curve for sifuvirtide in plasma was linear over a range of 4.88-5000 mu g/L, with correlation coefficients above 0.9923. After iv or sc administration, the observed peak concentrations of sifuvirtide were 10626 +/- 2886 mu g/L and 528 +/- 191 mu g/L, and the terminal elimination half-lives (T,12) were 6.3 +/- 0.9 h and 5.5 +/- 1.0 h, respectively. After sc, T-max was 0.25-2 h, and the absolute bioavailability was 49% +/- 13%. Sifuvirtide inhibited the syncytium formation between HIV-1 chronically infected cells and uninfected cells with an IC50 of 0.33 mu g/L. Conclusion: An on-line SPE-LC/MS/MS approach was established for peptide pharmacokinetic studies. Sifuvirtide was rapidly absorbed subcutaneously into the blood circulation. The T-1/2 of sifuvirtide was remarkably longer than that of its analog, enfuvirtide, reported in healthy monkeys and it conferred a long-term plasma concentration level which was higher than its IC50 in vitro.

A solid-phase microextraction fiber coated with diglycidyloxycalix[4]arene yields very high extraction selectivity and sensitivity during the analysis of chlorobenzenes in soil

A novel fiber coated with novel sol-gel (5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-diglycidyloxycalix[4]arene/hydroxy-terminated silicone oil; diglycidyloxy-C[4]/OH-TSO) was prepared for use with headspace solid-phase microextraction (HS-SPME) combined with gas chromatography (GC) and electron capture detection (ECD), which was applied in order to determine nine chlorobenzenes in soil matrices. Due to the improved fiber preparation, which increases the percentage of calixarene in the coating, the new calixarene fiber exhibits very high extraction selectivity and sensitivity to chlorine-substituted compounds. Various parameters affecting the extraction efficiency were optimized in order to maximize the sensitivity during the chlorobenzene analysis. Interferences from different soil matrices with different characteristics were investigated, and the amount extracted was strongly influenced by the matrix. Therefore, a standard addition protocol was performed on the real soil samples. The linear ranges of detection for the chlorobenzenes tested covered three orders of magnitude, and correlation coefficients > 0.9976 and relative standard deviations (RSD) < 8% were observed. The detection limits were found at sub-ng/g of soil levels, which were about an order of magnitude lower than those given by the commercial poly(dimethylsiloxane) (PDMS) coating for most of the compounds. The recoveries ranged from 64 to 109.6% for each analyte in the real kaleyard soil matrix when different concentration levels were determined over the linear range, which confirmed the reliability and feasibility of the HS-SPME/GC-ECD approach using the fiber coated with diglycidyloxy-C[4]/OH-TSO for the ultratrace analysis of chlorobenzenes in complex matrices.

Determination of phthalate acid esters plasticizers in plastic by ultrasonic solvent extraction combined with solid-phase microextraction using calix[4]arene fiber

Ultrasonic solvent extraction combined with solid-phase microextraction (SPME) with calix[4]arene/hydroxy-terminated silicone (C[4]/OHTSO) oil coated fiber was used to extract phthalate acid esters (PAEs) plasticizers in plastic, such as blood bags, transfusion tubing, food packaging bag, and mineral water bottle for analysis by gas chromatography (GC). Both extraction parameters (i.e. extraction time, extraction temperature, ionic strength) and conditions of the thermal desorption in a GC injector were optimized by analysis of eight phthalates. The fiber shows wonderful sensitivity and selectivity to the tested compounds. Owing to its high thermal stability (380 degreesC), the carryover effect that often encountered when using conventional fibers can be reduced by appropriately enhancing the injector temperature. The method showed linear response over two to four orders of magnitude with correlation coefficients (r) better than 0.996, and limits of detection (LOD) ranged between 0.006 and 0.084 mug l(-1). The relative standard deviation values obtained were less than or equal to 10%. bis-2-Ethylhexyl phthalate (DEHP) was the sole analyte detected in these plastics and recoveries were in the ranges 95.5-101.4% in all the samples. (C) 2004 Elsevier B.V. All rights reserved.

Contamination and distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in agriculture fields in Ya-Er Lake area, China

The contamination and distribution of polychlorinated dibeinizo-p-dioxins and dibenzofurans (PCDD/Fs) from two agricultural fields of a heavily polluted lake area in China (Ya-Er Lake) are presented. The vertical distribution pattern of total PCDD/Fs in soil cores reveals that the maximum concentration was in the layer of 20-30 cm. The concentrations in the top layer of soil at the two sites were similar (17.48 ng/kg at Site 1 and 18.10 ng/kg at Site 2), but the maximum concentration of Site 1 (120.8 ng/kg) was two times higher than that of Site 2 (64.39 ng/kg). The maximum concentration of PCDD/Fs in mud cores in rice fields (0-50 cm) at Sites 1 and 2 was in the layer of 0-10 cm. The maximum PCDD/F concentration in the top layer in mud at Site 1 (203.1 ng/kg) was higher than that at Site 2: (143.3 ng/kg). Significant correlations were found between the mind PCDD/Fs and the organic carbon content (R = 0.9743, P< 0,05 at Site 1; R = 0.9821, P< 0.05 at Site 2), the two variables being highly correlated (R = 0.9049, P< 0.05, at Site 1; R = 0.9916, P< 0.05 at Site 2). All correlation coefficients were significant at the 95% level. Concentrations were highly correlated with organic carbon, indicating that sorption to organic carbon was the dominant mechanism. Using principal component analysis, the homologue profiles of soil, mud, and plants (rice and radish) were compared. The PCDD/F patterns in plants were found not to be correlated to those in soil and mud. This suggests that atmospheric deposition may be the main source of PCDD/Fs in rice grain. However, mixed exposure involving uptake mechanisms and atmospheric deposition is considered main the source of PCDD/F pollution in radishes. (C) 2002 Elsevier Science (USA).

Prediction of the retentions of polybrominated dibenzo-p-dioxins (PBDDs) by using the retentions of polychlorinated dibenzo-p-dioxins (PCDDs)

The retention equations ln k' = A + B/T of 49 polychlorinated dibenzo-p-dioxins (PCDDs) and 4 polybrominated dibenzo-p-dioxins (PBDDs) in gas chromatography (GC) have been investigated to evaluate the properties of regression coefficients A and B. The quantitative relationships between A and B values of PCDDs and those of PBDDs are found. The regression equations derived have correlation coefficients greater than 0.997. The A, B values of any PBDD can be predicted by using the A, B values of the PCDD according to these relationships. Using these predicted A and B values, the retention times of all PBDDs can be predicted at any temperature program. It is very useful to identify the peak position of any PBDD because at present there are only a few standards of PBDDs available. (C) 2000 Elsevier Science Ltd. All rights reserved.

Quantitative relationship between chromatographic retentions and molecular structures of polychlorinated dibenzo-p-dioxins (PCDDs)

A new approach to study the quantitative relationships between chromatographic retentions and molecular structures of polychlorinated dibenzo-p-dioxins (PCDDs) is described. The retention equations of PCDDs log k' = A + B/T in gas chromatography (GC) are used to evaluate the properties of the regression coefficients A and B, which have been widely accepted as highly reliable chromatographic retentions. The quantitative relationships between the A, B values and the molecular structures are found. The molecular descriptors given for the first time in this article are very effective. As a result, the regression equations are derived with correlation coefficients greater than 0.9995. The A, B values of PCDDs with no standards available have been predicted according to these relationships. They are very useful in chromatographic identification. The retention times of all PCDDs can be conveniently predicted at any temperature program. Compared with the data obtained from the relevant experiments, the results of prediction are very accurate. (C) 2000 Elsevier Science Ltd. All rights reserved.

Biological evaluation of running waters in Korea, with special reference to bioassessment using the PFU system

A total of six stations in the Han River system were selected for establishing polyurethane foam units (PFUs) to collect protozoans, including phytomastigophorans, zoomastigophorans, amoebas and ciliates, in July 1993. In the bioassessment of microbial communities using the PFUs, the number of species decreased as pollution intensity increased. The diversity index values calculated at the main stations generally agreed with the pollution status of the stations. Anyang-Chon (Chon means stream) showed the lowest diversity value (1.89), and all stations, except Masok and Anyang-Chon, showed diversity index values ranging from 3.15 to 3.93. The highest heterotrophic index (HI) value was detected in Anyang-Chon followed by Masok-Chon. The number of species at the main stations reached a maximum on day 11 of being exposed to PFUs. The results of S-eq, G and T-90% all suggest that bioassessments using the PFU system were well matched with pollution status of the water. All microbial variables were significantly correlated with comprehensive chemical pollution indices, P-a and P-b, with correlation coefficients ranging from r=0.87 to r=0.96.

施肥水平对长武旱塬地冬小麦产量影响的模拟

为了在实时气象条件下确定旱塬区适宜的肥力水平和产量水平,在模拟精度验证基础上,应用WinEPIC模型模拟研究了黄土高原长武旱塬地1957～2001年期间不同肥力水平下连作冬小麦田产量效应。模型验证结果表明CK、N、NP处理产量模拟值与观测值之间的相关系数分别为0.740、0.764和0.740,均达到显著水平,WinEPIC模型对不同肥力处理下冬小麦籽粒产量模拟较为准确。模拟结果表明,无肥、低肥、中肥和高肥处理下连作冬小麦的产量均呈现波动性降低趋势,其平均值分别为1.055、1.422、2.405和3.170t/hm2,不同肥力处理间差异显著,以中肥和高肥处理增产效果最好。为黄土高原南部沟壑区旱地小麦生产的可持续发展提供了科学依据。

氮肥对黄瓜根际土壤线虫群落组成、结构及其多样性的影响

土壤线虫是土壤动物的主要功能类群之一，在土壤养分分解和循环中起到重要的作用。本研究通过施用两种形态氮肥，硝态氮(NO-3–N)和铵态氮(NH+4–N)，对黄瓜整个生长期内根际土壤线虫的群落组成、结构及其多样性等的影响进行了比较研究。为增进土壤健康，提高土壤质量以及合理施用氮肥提供科学的理论依据。研究结果如下： 1. 氮肥处理后，不同浓度NO-3–N处理提高了根际土壤线虫数量，而NH+4–N处理（202.5 kg N/ hm2）抑制了线虫数量的增加。线虫群落结构相对较稳定，营养类群变化不大。且少量优势科/属会对土壤线虫群落特征起着至关重要的作用。 2. 在整个生长季节内，非寄生线虫的群体动态变化与寄生线虫的群体的动态变化具有相反的变化趋势。其中，NO-3–N处理和NH+4–N处理后植物寄生线虫出现频率的变化趋势相近，都是由高到低；非植物寄生线虫出现频率的变化趋势则都是由低到高。这说明非植物寄生线虫数量增长和空间占位对植物寄生线虫群体有一定的抑制作用。另外，也反映了适量氮肥在一定程度上能够减轻植物寄生线虫对黄瓜的危害。 3. 由多样性指数变化可知，NO-3–N和NH+4–N在低肥（67.5 kg N/hm2）和高肥（202.5 kg N/hm2）处理较中肥（135.0 kg N/hm2）处理，更不利于提高土壤线虫多样性地提高和线虫群落的稳定性。中肥不同形态氮肥处理与对照相比，H´指数在初花期和结果期显著增加了土壤线虫的H´指数，说明施入两种形态的氮肥能够提高线虫生物多样性程度。NH+4–N处理在初花期和结果期显著降低了土壤线虫种类的丰富性。土壤线虫生物多样性变化中，H´和SR指数在一定程度上能够反映施用无机氮肥对土壤线虫的多样性的影响，而J指数和λ指数效果不明显。NO-3–N和NH+4–N处理相比较，NO-3–N处理对黄瓜土壤线虫的多样性指数影响更大，促进了土壤线虫群体的多样化和种类的丰富度，更有利于提高土壤线虫的多样性，增加其稳定性。这些结果表明适量无机氮肥特别是NO-3–N的施用对黄瓜土壤线虫的生物多样性有一定的维护和提高作用。 4. 线虫数量与土壤质量指标的相关分析表明：线虫数量与有关土壤理化生指标，如土壤NO-3–N、NH+4–N、有机质含量等的正相关程度高，与总酚含量等显著负相关；与根际土壤微生物，细菌、真菌、放线菌数量等呈显著正相关。另外，线虫数量与土壤含水量未表现出显著相关关系。 Nematodes play a major role in decomposition and nutrient cycling in soil. Nematode community analyses are useful in assessing soil ecosystem status and function. The effects of two forms of mineral nitrogenous fertilizers (NO-3–N and NH+4–N) on nematode community composition, structure and diversity in rhizosphere of cucumber were investigated during different growing seasons of cucumber. Systematically research of effects of nitrogenous fertilizers could help to obtain better undstanding of a healthy soil and using nitrogenous fertilizers in reason. The main results are as follows: 1. The total numbers of nematode were more abundant in NH+4–N treatments than other teatments. However, NH+4–N teatment（202.5 kg N/hm2）dramatically inhibited it. All the tropic groups in the soil nematode communities were stable, and the dominant family or genus had an important function in the nematode community structure. 2. There was similar trend of the frequency of plant parasitic nematodes between NO-3–N and NH+4–N treatment, the similar trend of the frequency of non-plant parasitic nematodes was also found. But the frequency of plant parasitic nematodes exhibited a contrary trend to that of plant parasitic nematodes after different nitrogenous fertilizer treatments. The results showed that the increasing trend of the frequency and the niche of non-plant parasitic nematodes inhibited the plant parasitic nematodes, and indicated that right chemical fertilizers dosage could abate plant parasitic nematodes harm to cucumber. 3. The changes of the biodiversity index showed that the nitrogen treatment（135.0 kg N/hm2）promoted the stabilization of soil nematode diversity than other nitrogen treatments(67.5 kg N/hm2 and 202.5 kg N/hm2). In the treatment（135.0 kg N/hm2）,The changes in nematode diversity between the control plots and treated plots were compared by the biodiversity index (H´, J, SR, λ). Among these tested index, H´ and SR were effective in reflecting the effects of different nitrogenous fertilizers on the diversity of soil nematodes. In comparison with the NH+4–N treatment, the NO-3–N treatment promoted the stabilization of soil nematode diversity. 4. Correlation coefficients between nematode abundance and soil quality indices indicated that the total numbers of nematode were affected positively by NO-3–N, NH+4–N and the organic matter, and negatively by total phenolic acids; the total num- bers of nematode had positive correlation with bacteria, fungi and actinomycetes nu- mbers. Soil water contents had only a weak negative influence on it.

川西亚高山针叶林主要针叶树种年轮生态学研究

米亚罗地区是四川西部较为典型的亚高山针叶林区域之一。为建立该地区主要针叶树种岷江冷杉、云杉、紫果云杉和红杉的年轮宽度年表资料，了解不同海拔高度岷江冷杉原始林和不同恢复过程的人工针叶林及次生混交林树木径向生长规律，结合样地调查，用生长锥钻取了树木芯样做年轮生态学分析。芯样经过标准化程序固定和打磨抛光后，用WinDENDRO图像分析系统测量年轮宽度序列，用COFECHA程序交叉定年和控制测量数据质量，用ARSTAN程序建立了4个主要针叶树种的地区年表和不同海拔高度岷江冷杉林及人工针叶林和次生混交林针叶树的样地年表。 4个主要针叶树种年轮宽度年表的平均敏感度低于0.2，而其晚材宽度年表都具相对较高的平均敏感度。早材宽度与年轮总宽度标准化年表间的相关系数均在0.9以上；晚材宽度与年轮总宽度标准化年表间的相关系数则种间差异较大，红杉的最高，岷江冷杉的最低。岷江冷杉晚材宽度与年轮总宽度的相关性从1970年以后明显下降，而其他种的相关系数则随时间变化较小。树种之间标准化年表显著正相关，而云杉与紫果云杉和红杉与岷江冷杉之间相关系数明显较高。年表序列的第1主分量表达了4个树种树木共同径向生长变化格局；第2至第4主分量分别表达了云杉属和冷杉属、常绿针叶树种和落叶针叶树种以及云杉和紫果云杉树木径向生长变化差异。 不同海拔高度的8个岷江冷杉样地年轮宽度年表序列敏感度大体上随海拔高度升高而降低。各样地早材宽度与年轮总宽度年表之间的相关系数均在0.9以上，且随海拔高度变化不大；晚材宽度与年轮总宽度之间的相关系数随海拔高度的变化较大，并有随海拔升高而降低的趋势。样地年表序列之间相关系数差异很大，高海拔样地年表间多为显著正相关；低海拔样地年表间的相关系数变化不一；高海拔和低海拔样地年表之间相关性较差，且多不显著。样地年表的第1主分量能解释年表序列总方差的37.5%，反映了不同海拔高度岷江冷杉林木共同的径向生长变化格局；第2和第3主分量分别解释总方差的24.5%和18.2%，表现出明显的高海拔和低海拔样地树木间不同的径向生长变化，除一些样地例外，它们一般与低海拔样地年表有正相关，与高海拔样地年表有负相关。在那些另外的样地，海拔以外的其他因素可能也影响了树木径向生长变化。不同海拔高度样地林木的生长抑制和生长释放频率在不同时期表现出较大的差异，表明了不同的干扰历史和林木补充时间。 人工针叶林和次生混交林各样地林木早材宽度与其年轮总宽度年表之间相关系数均高达0.9以上；晚材宽度与年轮总宽度年表之间也都显著正相关，但人工针叶林样地的明显较高。样地年表序列之间的相关关系表现为，林分起源和经营管理相似的样地年表之间的相关系数明显较高，如人工针叶林与人工针叶林尽管树种不同，但样地年表之间显著正相关，而与次生混交林样地年表间关系不显著；反之亦然。综合比较各项生长参数及不同时期的树木径向生长速率，人工针叶林树木的胸径增长至少在40年以内是优于次生混交林的同种（或不同种）针叶树的。不同样地林木生长释放和生长抑制及人工针叶林树木胸高断面积增长分析表明，除严重的人为干扰外，林分郁闭后林木密度过大是造成高频率生长抑制的主要原因，在林分发育的适当时期通过抚育间伐等措施调控林分密度，是保证林木胸高断面积在一定时期内保持较高的连年增长的关键。日本落叶松作为引进的树种，在海拔3100 m左右种植表现良好，近30年来各项生长指标均高于林龄相近的云杉人工林，因此，适当用其作为川西亚高山针叶林采伐迹地快速恢复是合理的。 Miyaluo area is one of the typical regions covered by subalpine coniferous forests in western Sichuan province of southwestern China. To develop the regional tree-ring width chronology series for the dominant conifers such as Abies faxoniana, Picea asperata, P. purpurea and Larix potaninii, and to understand the radial growth patterns of conifers in Abies faxoniana natural forest stands at different altitudes, and in coniferous plantations and natural regenerated mixed stands in their different restoring processes as well, increment cores were sampled in the field together with conventional plots investigations for dendroecological analyses. After the increment cores being prepared according to standard procedures, the ring widths (total-ring and intra-ring widths) were measured with a WinDENDRO image-analysis system, and the measured tree-ring sequences were crossdated and quality-controlled with the software COFECHA. Using the software ARSTAN, we developed tree-ring width based chronology series of the four dominant conifers, eight site-specific Abies faxoniana chronologies, and seven site-specific chronologies of conifers in coniferous plantations and natural regenerated mixed stands. Mean sensitivities for total ring width chronologies of the four sampled dominant conifers were all below 0.2, while those for the latewood width chronologies of the same species were relatively much higher. Correlation coefficients between standard earlywood and total ring width chronologies of the four conifers were all above 0.9, but those between standard latewood and total ring width chronologies exhibited differences among species, with the coefficient of Larix potaninii the highest and that of Abies faxoniana the lowest. Correlation coefficients between latewood and total ring width of A. faxoniana obviously decreased from 1920-1970 for successive 50-year segments with 10-years lag analyses, though the same for the other three species changed unnoticeably with time. Tree-ring standard chronologies among species showed significant positive correlations, with the correlation coefficients between chronologies of Picea asperata and P. purpurea, and of Larix potaninii and Abies faxoniana relatively much higher. The first principal component of tree-ring chronologies represented the common radial growth patterns of the four conifers in Miyaluo area. The second, third and fourth PCs expressed the differences in radial growth responses for the genus Picea and Abies, for the evergreen and deciduous confers, and for the two species of the genus Picea, respectively. In general, mean sensitivities of the eight Abies faxoniana site-specific tree-ring width chronologies decreased with increasing altitude. The correlation coefficients between earlywood and total ring width chronologies for all sites reached 0.9, which did not change much with altitude; but those between latewood and total ring width chronologies diversified, with a decreasing tendency from lower altitudinal sites to higher altitudinal sites. Correlation coefficients among site chronologies varied considerably, with significant positive correlations among higher site chronologies, mixed results among lower site chronologies, and poor and insignificant correlations between chronologies of higher site and lower site. The first PC, which represents 37.5% of the total variance, reflected a common radial growth response at sites of different altitudes, and it showed a tendency of explaining more variance with increasing altitude. The second and the third PCs contributed to 24.5% and 18.2% of the total variance, respectively, exhibiting distinctive differences in radial growth responses between low- and high-altitudinal sites. With some exceptions, the radial growth represented by the second and third PCs had a positive correlation with that at the low-altitudinal sites and a negative correlation with that at the high-altitudinal sites. For those exceptional sites, factors other than altitude might also play a role in affecting tree-ring growth variations. Trees in stands of different altitudes showed great differences in frequencies of growth suppressions and releases through times, suggesting different disturbance histories and periods when trees recruiting to the canopy. Correlation coefficients between earlywood and total ring width chronologies for all sites of coniferous plantations and natural regenerated mixed stands were also above 0.9; and the same between latewood width and total ring width chronologies all positively correlated, too, with the coefficients of the coniferous plantations obviously much higher. Correlations among site chronologies showed that the coefficients among sites with similar stand origin and management regimes were much higher than those among sites with different stand origin and management regimes. For example, significant positive correlations were found for chronologies among different coniferous plantations, irrespective of species differences; while insignificant correlations between chronologies of the same conifer from a coniferous plantation and a natural regenerated mixed stand, and vise versa. Integrative comparisons of different tree growth parameters and radial growth rates at different stages indicated that the diameter at breast height (DBH) increments for trees in coniferous plantations were faster than those for trees of the same (or different) species in the natural regenerated mixed stands, at least within their first 40 years of stand development. Analyses of growth releases and suppressions, and basal area increments of trees in different stands demonstrated that over-dense individuals after canopy closure was the main factor resulting in high frequencies of radial growth suppressions, with some exceptions of severe man-made disturbances. Therefore, to ensure a continuous basal area current annual increment in certain periods, tree density controlling through thinning in due time during the stand development process are necessary. It should be mentioned that, as an introduced conifer to Miyaluo area, Larix kaempferi grew quite well at altitude of ca. 3100 m after planting in 1970s. In their near 30 years of stand development, Larix kaempferi trees exhibited faster growth in various parameters than Picea asperata trees of the similar stand age did. Thus we think it reasonable to use Larix kaempferi as a fast restoring species at appropriate sites of cutting blanks of subalpine coniferous forests in western Sichuan.

Biosorption of uranium by chemically modified Rhodotorula glutinis

The present paper reports the biosorption of uranium onto chemically modified yeast cells, Rhodotorula glutinis, in order to study the role played by various functional groups in the cell wall. Esterification of the carboxyl groups and methylation of the amino groups present in the cells were carried out by methanol and formaldehyde treatment, respectively. The uranium sorption capacity increased 31% for the methanol-treated biomass and 11% for the formaldehyde-treated biomass at an initial uranium concentration of 140 mg/L The enhancement of uranium sorption capacity was investigated by Fourier transform infrared (FTIR) spectroscopy analysis, with amino and carboxyl groups were determined to be the important functional groups involved in uranium binding. The biosorption isotherms of uranium onto the raw and chemically modified biomass were also investigated with varying uranium concentrations. Langmuir and Freundlich models were well able to explain the sorption equilibrium data with satisfactory correlation coefficients higher than 0.9. (C) 2010 Elsevier Ltd. All rights reserved.